Which missing line of code would place the text on top of the image?

<div class=”container”>
<img src=”grumpy-cat.gif” />
<p>The z-index property is cool!</p>
</div>
img {
position: absolute;
left: 0px;
top: 0px;
// Missing line
}

• z-index: 1;
• z-index: -1;
• z-index: 0;
• z-index: true;